1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive detecting disk warping by detecting a negative correlation between read signal amplitudes from top and bottom disk surfaces.
2. Description of the Prior Art
Disk drives typically include one or more disks that are clamped to a hub of a spindle motor. As the spindle motor rotates the disks, an air bearing forms between the disk surfaces and the heads so that the heads are said to “fly” just above the disk surface, wherein the read signal amplitude (and associated read signal quality) varies inversely with the fly-height of the head. Certain influences may cause a warping of the disk, for example, a particle contaminant may get caught between the clamp and the disk during the clamping process, or the disk itself may be warped due to a manufacturing defect. If the warping is significant, the resulting fluctuations in the read signal amplitude may render the disk drive inoperable.
There is, therefore, a need to repair or discard disk drives with a disk warping that exceeds a reliability threshold, for example, during manufacturing to prevent defective disk drives from entering the market.